Phenolic compounds, antioxidant and heavy metals in rhubarb of Iraq Kurdish Region and Siirt

This study aimed to find out the concentration of thirty metals (Li, Be, B, Na, Mg, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Sn, Sb, Ba, La, Ce, Pt, Tl and Pb), compare the levels of them and subjected to various chemometric analysis between metal contents and place of cultivated Rhubarb for classification purposes. Samples were collected from Iraqi Kurdish Region (Sor, Rash, Karajar, Gara and Qalandar) and Siirt, Turkey (Pervari and Şirvan). After acid digestion of samples by the microwave, metal analysis was carried out with ICP-MS (Thermo Scientific ICAP Q ICP-MS) instrument. The metals and places of cultivated were classified with principal component analysis (PCA) and cluster analysis (CA) as classification techniques. In addition, total phenolic content, total flavonoid amount, antioxidant activity, and phenolic profiles of methanol extract of Rheum ribes collected from Iraqi Kurdish Region and Siirt were examined. Total phenolic content was assessed by Folin Ciocalteau's method and varied between 84.02-387.53 µg gallic acid/mL of extract. Furthermore, total flavonoid content was determined by the aluminum chloride colorimetric method and varied 69.98-935.75 rutin μg mL-1 extract. The antioxidant potency was determined by using FRAP and DPPH methods. In FRAP assay, the highest antioxidant activity (IC50) was found 25.18±0.04 μg mL-1 extract. In DPPH method,the maximum percentage inhibition was found 88.11%. Metal chelating activity was estimated by method of Rival et al, 2001.It was observed that all the samples were over than 70%. Finally phenolic compounds profiles also were determined by LC-MS/MS instrument. In this step total of 37 phenolic compounds in extracts were analyzed, but 26 of them were detected as qualitative and quantitatively. Malic acid (15.72±0.53 mg g-1 extract) and Rutin (76.93±0.03 mg g-1 extract) were identified as the major phenolic compounds. The results of the study confirm that these samples have potential biological activities and can be introduced as important sources of natural antioxidants.